1. Field of the Invention
The present invention relates generally to methods and apparatus for the thermal ablation of hollow body organs, such as the gallbladder. In particular, the present invention relates to a catheter structure having a heating element at its distal end, where the catheter may be used to introduce an unheated thermally-conductive medium to the hollow body organ, and the heating element used to heat the medium in situ in order to destroy the endothelial lining or mucous membrane of the organ.
Heretofore, it has frequently been necessary to perform open surgery in order to remove diseased body organs, such as gallbladders, appendixes, and the like. For example, the current treatment for cholecystolithiasis (gallstone disease) involves the surgical removal of the gallbladder, referred to as a cholecystectomy. As with all major surgical procedures, the patient is exposed to the risk of trauma, infection, general anesthetic, as well as requiring extended recuperation time. It would therefore be desirable to provide for therapies for diseased organs which can effectively eliminate the organ without the necessity of open surgical intervention.
In recent years, a number of therapies have been developed as an alternative to open surgery, often referred to as "least invasive surgery." While least invasive surgical procedures have no fixed definition, they are generally characterized by the use of specialized surgical tools in combination with visual or radiographic imaging techniques. The specialized tool is generally inserted through an open body orifice or a small surgical incision, and the tool is then positioned within the body using the imaging technique to allow manipulation of the affected organ or structure. A common example of least invasive surgery is arthroscopic knee surgery where penetration of the surgical tools is minimal. Less accessible body organs, such as the heart and interior blood vessels, may be reached by specialized catheters which may be routed through the vascular system over relatively long distances. Typical of such vascular catheters are balloon dilatation catheters which are used to expand regions of stenosis within diseased blood vessels.
For the above reasons, it would be desirable to provide least invasive surgical methods and apparatus for the destruction or ablation of diseased hollow body organs, such as the gallbladder, the appendix, the uterus, and the like. Such methods and apparatus should also be suitable for the treatment of relatively small body structures, such as blood vessels, and should be able to effect ablation without undue risk to surrounding body tissues and structures. In particular, the method and apparatus should be able to provide for the controlled application of thermal energy in order to destroy the hollow body organ with a minimal chance of regeneration. Desirably, the apparatus should be sufficiently small and flexible to allow introduction through and into constricted ducts and passages adjoining the hollow body organ, and the apparatus should be capable of delivering a non-linear heat flux which varies depending on position within the hollow body organ and/or connecting duct. Such non-linear heat flux will allow control of the amount of heat delivery to particular regions within the organ and/or duct.
2. Description of the Background Art
Coleman, Non-Surgical Ablation of the Gallbladder, Proc. 1988 SCVIR, pp 214-219, is a review article discussing various techniques for non-surgical gallbladder ablation, including the work of Salomonowitz and of Getrajdman relating to the introduction of an externally heated medium to induce fibrosis of the gallbladder. The article further presents data demonstrating thermal ablation of a dog's gallbladder after open surgical injection of hot contrast media. The work of Salomonowitz is described in Salomonowitz et al. (1984) Arch. Surg. 119:725-729. The work of Getrajdman is described in Getrajdman et al. (1985) Invest. Radiol. 20:393-398 and Getrajdman et al. (1986) Invest. Radiol. 21:400-403. The use of sclerosing agents to induce gallbladder fibrosis is described in Remley et al. (1986) Invest. Radiol. 21:396-399. See also Becker et al. (1988) Radiology 167:63-68. U.S. Pat. No. 4,160,455, describes a device for internally heating a body cavity for therapy, where the heat is intended to inhibit the growth of tumor cells. German Patent 37 25 691 describes a catheter combining a heater at its distal tip and a balloon proximate the heater, where the heater is not directly exposed to the fluid environment surrounding the catheter tip. U.S. Pat. No. 4,869,248, describes a thermal ablation catheter having a resistive heating loop at its distal end. Other patent documents describing heated or cooled catheters include U.S. Pat. Nos. 4,676,258; 4,638,436; 4,469,103; 4,375,220; 3,901,224; USSR 1329-781-A; and USSR 281489.